Estrogen has been implicated in the incidence of breast cancer. This could be due to the profile and level of different estrogens in the body which are controled by its metabolism by alternative pathways. The inter- individual differences in the expression & activity of the enzymes involved in this metabolism can therefore act as susceptibility risk factor for breast cancer. Consequently, modulation of estrogen metabolism to favorably alter the profile & level of estrogens in the body can be used as a mgmt strategy. This project will investigate this ability.